Fast ack/nack in wireless communication networks

ABSTRACT

A receiver is configured to receive and process a radio signal. The radio signal includes a first frequency band including a first signal, the first signal including a plurality of TDD-frames. The receiver is configured to evaluate reception of downlink data to obtain evaluation data. The receiver is further configured to transmit the evaluation data in a second frequency band outside of the first frequency band.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/388,406 filed on Apr. 18, 2017 which is a continuation ofInternational Application No. PCT/EP2017/076776, filed Oct. 19, 2017,which is incorporated herein by reference in its entirety, andadditionally claims priority from European Application No. EP16195299.9, filed Oct. 24, 2016, which is also incorporated herein byreference in its entirety.

The present invention concerns the field of wireless communicationnetworks or systems, more specifically wireless communication networksor systems to be accessed by time-division multiplexing. The inventionfurther concerns narrowband HARQ. Embodiments concern receivers thatallow for a fast retransmission of error-prone data.

BACKGROUND OF THE INVENTION

Mobile communication networks are used for transmitting and/or receivingdata from or to wireless communication nodes such as user equipmentand/or IoT devices. IoT devices may include physical devices, vehicles,buildings and other items having embedded therein electronics, software,sensors, actuators, or the like as well as network connectivity thatenable these devices to collect and exchange data across an existingnetwork infrastructure.

FIG. 1 is a schematic representation of an example of such a networkinfrastructure, like a wireless communication system including aplurality of base stations eNB₁ to eNB₅, each serving a specific areasurrounding the base station schematically represented by the respectivecells 100 ₁ to 100 ₅. The base stations are provided to serve userswithin a cell. A user may be a stationary device or a mobile device.Further, the wireless communication system may be accessed by IoTdevices which connect to a base station or to a user. FIG. 1 shows anexemplary view of only five cells, however, the wireless communicationsystem may include more such cells. FIG. 1 shows two users UE₁ and UE₂,also referred to as user equipment (UE), that are in cell 100 ₂ and thatare served by base station eNB₂. Another user UE₃ is shown in cell 100 ₄which is served by base station eNB₄. The arrows 102, 102 ₂ and 102 ₃schematically represent uplink/downlink connections for transmittingdata from a user UE₁, UE₂ and UE₃ to the base stations eNB₂, eNB₄ or fortransmitting data from the base stations eNB₂, eNB₄ to the users UE₁,UE₂, UE₃. Further, FIG. 1 shows two IoT devices 104 ₁ and 104 ₂ in cell100 ₄, which may be stationary or mobile devices. The IoT device 104 ₁accesses the wireless communication system via the base station eNB₄ toreceive and transmit data as schematically represented by arrow 105 ₁.The IoT device 104 ₂ accesses the wireless communication system via theuser UE₃ as is schematically represented by arrow 1052.

The wireless communication system may be any single-tone or multicarriersystem based on frequency-division multiplexing, like the orthogonalfrequency-division multiplexing (OFDM) system, the orthogonalfrequency-division multiple access (OFDMA) system defined by the LTEstandard, or any other IFFT-based signal with or without CP, e.g.DFT-SOFDM. Other waveforms, like non-orthogonal waveforms for multipleaccess, e.g. filterbank multicarrier (FBMC), may be used. Othermultiplexing schemes like time-division multiplexing (time-divisionduplex—TDD) may be used.

An OFDMA system for data transmission may include an OFDMA-basedphysical resource grid which comprises plurality of physical resourceblocks (PRBs) each defined by 12 subcarriers by 7 OFDM symbols andincluding a set of resource elements to which various physical channelsand physical signals are mapped. A resource element is made up of onesymbol in the time domain and one subcarrier in the frequency domain.For example, in accordance with the LTE standard a system bandwidth of1.4 MHz includes 6 PRBs, and the 200 kHz bandwidth in accordance withthe NB-IoT enhancement of the LTE Rel. 13 standard includes 1 PRB. Inaccordance with LTE and NB-IoT, the physical channels may include thephysical downlink shared channel (PDSCH) including user specific data,also referred to as downlink payload data, the physical broadcastchannel (PBCH) including for example the master information block (MIB)or the system information block (SIB), the physical downlink controlchannel (PDCCH) including for example the downlink control information(DCI), etc. The physical signals may comprise reference signals (RS),synchronization signals and the like. The LTE resource grid comprises a10 ms frame in the time domain having a certain bandwidth in thefrequency domain, e.g. 1.4 MHz. The frame has 10 subframes of 1 mslength, and each subframe includes two slots of 6 or 7 OFDM symbolsdepending on the cyclic prefix (CP) length.

FIG. 2 shows an exemplary LTE OFDMA-based subframe with two antennaports for different selected Tx antenna ports. The subframe includes tworesource blocks (RB) each made up of one slot of the subframe and 12subcarriers in the frequency domain.

The subcarriers in the frequency domain are shown as subcarrier 0 tosubcarrier 11, and in the time domain, each slot includes 7 OFDMsymbols, e.g. in the slot 0 OFDM symbols 0 to 6 and in slot 1 OFDMsymbols 7 to 13. The white boxes 106 represent resource elementsallocated to the PDSCH including the payload or user data, also referredto a payload region. The resource elements for the physical controlchannels (including non-payload or non-user data), also referred to thecontrol region, are represented by the hatched boxes 103. In accordancewith examples, resource elements 103 may be allocated to the PDCCH, tothe physical control format indicator channel (PCFICH), and to thephysical hybrid ARQ indicator channel (PHICH). The cross-hatched boxes107 represent resource elements which are allocated to the RS that maybe used for the channel estimation. The black boxes 108 represent unusedresources in the current antenna port that may correspond to RSs inanother antenna port. The resource elements 103, 107, 108 allocated tothe physical control channels and to the physical reference signals arenot evenly distributed over time. More specifically, in slot 0 of thesubframe the resource elements associated with the symbol 0 and thesymbol 1 are allocated to the physical control channels or to thephysical reference signals, no resource elements in the symbols 0 and 1are allocated to payload data. The resource elements associated withsymbol 4 in slot 0 as well as the resource elements associated withsymbols 7 and 11 in slot 1 of the subframe are allocated in part to thephysical control channels or to the physical reference signals. Thewhite resource elements shown in FIG. 2 may include symbols associatedwith payload data or user data and in the slot 0 for symbols 2, 3, 5 and6, all resource elements 106 may be allocated to payload data, whileless resource elements 106 are allocated to payload data in symbol 4 ofslot 0, and no resource element is allocated to payload data in symbols0 and 1. In slot 1, the resource elements associated with symbols 8, 9,10, 12 and 13 are all allocated to payload data, while for symbols 7 and11 less resource elements are allocated to payload data.

Data blocks may be coded, transmitted, received and decoded. Data whichhas been split up into a plurality of blocks for block-wise transmissionmay be buffered for reception until all blocks are received by thereceiver. One or more of those data blocks might be lost or might bereceived error-prone such that a retransmission of one or more datablocks may be needed. Such a retransmission may be initialized by theHARQ (Hybrid Automatic Repeat request) process.

Wherein in case of FDD (Frequency Division Duplex), it is pretty simpleand obvious for user equipment to transmit HARQ ACK (Acknowledge) orNACK (not/negative Acknowledgement), as the UE starts preparing theresponse as soon as it completes the decoding PDSCH and transmits it 4milliseconds (4 transmission time intervals—TTIs) later. But in TDD(Time Division Duplex), a UE cannot transmit the response in such afixed timing as in FDD. It has to wait until it gets the next chance forthe uplink (UL) transmission and the next chance will be differentdepending on UL/DL configuration (DL=downlink). Even when the UE getsthe chance to transmit on the UL, it may not be possible for theparticular UE to transmit all the response data. For example, if the UEgets too many DL subframes before the UL subframe, it will be difficultto transmit all the reply in the UL transmission because capacity orbandwidth of the physical uplink control channel (PUCCH) may not belarge enough to accommodate or piggyback all the HARQ ACK/NACK. Thus,especially when using TDD (e.g. in LTE frame structure type 2), the HARQprocess is only triggered after the next download. This takes at least 5ms in current LTE. Additionally this increases the HARQ buffers as alarge amount of data has to be stored until it can be successfullypassed onto the higher layers.

FIG. 3 a illustrates such a scenario in which an LTE system is runningframe structure type 2 (FS2) which is TDD with configuration 3 in FIG. 3b . Knowing this, the ACK/NACK timing can be derived from FIG. 4 , seeconfiguration #1. In LTE a frame may comprise ten subframes 202 ₀-202₉.In TDD all resource elements available for data transmission may be usedfor a specific purpose such as uplink or downlink data transfer or forspecial purpose such as subframe 202 ₁ allowing for special signaling inthe system and/or used as a guard time. With respect to the teachingsdisclosed herein, the special frames are considered as frames unusablefor uplink-purpose or downlink-purpose, wherein downlink-subframes anduplink-subframes are usable by the transmitter and receiver. The exampletransmission illustrated in FIG. 3 comprises a transmission from a basestation (evolved Node B—eNB) to an user equipment UE. Transmission insubframe 5, the subframe being referenced with 202 ₅ is disturbed suchthat the user equipment is unable to successfully decode the data.Disturbance may be understood as a lost package or a number of biterrors exceeding bit error correction ability of the used code.

During the following subframes 202 ₆-202 ₀ the user equipment is unableto report the disturbed transmission. In subframe 202 ₁ of thesubsequent frame and following the downlink subframes, the userequipment is able to transmit a NACK message indicating the error-pronetransmission. Two different mechanism to handle ACK messages in TDD areprovided: multiplexing and bundling. Multiplexing implies thatindependent acknowledgements for several received transport blocks arefed back to the eNB.

Bundling implies that the outcome of the decoding of downlink transportblocks from multiple downlink subframes can be combined into a singleHARQ-ACK and transmitted in the uplink. The data received in subframe nwill most likely be acknowledged in subframe n+4 at the earliest time.

Retransmission of the data is performed at the first following downlinksubframe 202 ₅ at the earliest.

FIG. 4 shows a table illustrating a timing of HARQ responses fordifferent UL/DL configurations in LTE. The table illustrates in whichsubframes n a HARQ response is transmitted and to which PDSCH theresponse relates to. The number inserted into a field relating to asubframe indicates the number of preceding subframes to which themessage relates. For example, in the case of UL/DL configuration 0ACK/NACK messages are transmitted at subframes 2, 4, 7 and 9. Atsubframe 2, the table shows the value 6. This means that the UEtransmits an ACK/NACK for PDSCH it received at 6 subframes earlier. Thusin subframe 2 only 2 subframes have been past in the current frame, buta frame comprises, for example, 10 subframes. Thus, 2+10 subframes haveto be considered and 6 subframes earlier was the 6^(th) subframe of theprevious frame (subframe 2+10-6 subframes=subframe 6). At subframe 4,the value 4 indicates that UE transmits ACK/NACK for PDSCH it receivedat subframe 0 in the current frame (subframe 4-4 subframes). At subframe7, the user equipment transmits ACK/NACK for PDSCH it received atsubframe 1 in the current frame (subframe 7-6 subframes). At subframe 9,the user equipment transmits ACK/NACK for PDSCH it received at subframe5 (subframe 9-4 subframes) in the current frame. Simplified, this meansthat a HARQ response can be sent at the earliest in the next ULsubframe, sometimes later.

Another way to transmit acknowledges is the physical HARQ indicatorchannel (PHICH) in the downlink which carries hybrid ARQ (HARQ)acknowledgements (ACK/NACK) for uplink data transfers. PHICHs arelocated in the first OFDM symbol of each subframe. The followingexplanation is given for the scenario on using FDD frame structure andthe normal PHICH duration according to LTE. A PHICH may be carried byseveral Resource Element Groups (REGs). Multiple PHICHs can share thesame set of REGs and are differentiated by orthogonal covers. PHICHswhich share the same resources are called a PHICH group. Consequently, aspecific PHICH is identified by two parameters: the PHICH group numberand the orthogonal sequence index within the group.

For determining how many REGs a PHICH needs, the following informationmay be taken into account. The channel coding for HARQ ACK/NACKs isstraightforward: an ACK is represented by three bits “111”, and a NACKis represented by 3 bits “000” (3 bits each). PHICHs use binaryphase-shift keying (BPSK) modulation, so 3 modulation symbols aregenerated for each ACK or NACK. Next, these 3 modulation symbols aremultiplied to the orthogonal cover, which has the spreading factor (SF)of 4 for the normal cyclic prefix, resulting in a total of 12 symbols.Each REG contains 4 resource elements REs and each RE can carry 1modulation symbol, so 3 REGs are needed for a single PHICH.

FIG. 5 illustrates an example of how PHICHs may be mapped to resources,wherein three PHICH groups are shown. The 3 REGs that support a PHICHgroup are evenly distributed within the system bandwidth to providefrequency diversity. The Physical Control Format Indicator Channel(PCFICH) also appears in the first symbol of each subframe and occupies4 REGs regardless of the system bandwidth. These 4 REGs are evenlydistributed across the system bandwidth.

A number of PHICHs that a PHICH group may include may be determined in away that a total of 8 orthogonal sequences have been defined in 3GPP TS36.211 table 6.9.1-2, so each PHICH group can carry up to 8 PHICHs.

$\begin{matrix}{N_{PHICH}^{group} = \left\lceil {{Ng}\left( {N_{RB}^{DL}/8} \right)} \right\rceil} & {{for}{normal}{CP}} \\{N_{PHICH}^{group} = {2 \times \left\lceil {{Ng}\left( {N_{RB}^{DL}/8} \right)} \right\rceil}} & {{{for}{extended}{CP}},{wherein}} \\{{Ng} \in \left\{ {\frac{1}{\epsilon};\frac{1}{2};1;2} \right\}} & {{signaled}{in}{MIB}}\end{matrix}$

FIG. 6 illustrates a number of PHICH groups with 10 MHz channelbandwidth dependent from the parameter Ng for normal cyclic prefixesaccording to the formula above. A number of PHICH groups that aresupported in a system depends on the specific configuration. The actualnumber of PCFICH groups can be derived from the downlink bandwidth andthe parameter Ng, both of which are broadcast in the MIB. The formula isdefined in 3GPP TS 36.211 section 6.9 as shown above. Assume that thedownlink channel bandwidth is 10 MHz and that Ng=1. In this case, therewill be a total of 7 PCFICH groups available. The total number ofPCFICHs supported per subframe would then be 7 PCFICH groups×8 PHICHsper PHICH group=56 PCFICHs. The total number of resource elements REsneeded is 7 PHICH groups×3 REGs or PHICH group×4 REs per REG=84 REs.

Each PCFICH may carry HARQ/NACKs for uplink data transfers. A UE knowswhere to look for its PHICH as in the time domain, if the uplinktransmission occurs in subframe n, the corresponding PHICH will be insubframe n+4. In the frequency domain, it is indicated by the uplinkresource allocation with DCI format 0, where the specific PHICH (PHICHgroup number, orthogonal sequence index within the group) is derivedfrom the lowest PRB index in the first slot of the corresponding PUSCHtransmission and the DMRs cyclic shift. This is defined in 3GPP TS36.213, section 9.1.2.

The parameter Ng is included in the MIB and not included in the SystemInformation Block (SIB) due to the reason that the UE needs to knowwhere the PCFICH configuration at the very beginning of the systemacquisition process, which is a “chicken-and-egg” problem. On one hand,the UE needs to decode PHICH to know where to find SIB on PDSCH. On theother hand, PDCCH and PHICH and PCFICH share the resources in thecontrol region of a subframe and the set of the available resources forPDCCH depends on the PHICH configuration as PCFICH resources are fixedand known.

Another way for transmitting ACK/NACK is the physical uplink controlchannel carrying downlink data acknowledgements. The physical uplinkcontrol channel (PUCCH) carries a set of information called UplinkControl Information (UCI). This is similar to PUCCH which carries DCI(Downlink Control Information). Depending on what kind of informationthe UCI in PDCCH carries, PDCCH is classified into various formations.In 3GPP 36.213, section 10.1 UE procedure for determining physicaluplink control channel assignment, the PUCCH format is summarized asfollows:

-   -   HARQ-ACK using PUCCH format 1a or 1 b    -   HARQ-ACK using PUCCH format 1 b with channel selection    -   Scheduling request (SR) using PUCCH format 1    -   HARQ-ACK and SR using PUCCH format 1a or 1 b    -   CQI using PUCCH format 2    -   CQI and HARQ-ACK using PUCCH format    -   2a or 2b for normal cyclic prefix    -   2 for extended cyclic prefix

FIG. 7 is a tabular describing the specification described above in 3GPPspecification, wherein FIG. 8 is another tabular format of descriptionof specification to illustrate the contents of ARQ and CSI. These tablesshow the type and length of uplink control information (UCI) messagessent over the physical uplink control channel (PUCCH) and can be seen asthe types of information that will instead be sent over the narrowbandcontrol channel as described in herein. The PUCCH format will be adoptedto the narrowband characteristic accordingly.

Thus, there is a need to enhance data exchange in mobile communicationnetworks.

Summary

An embodiment may have a receiver, wherein the receiver is configured toreceive and process a radio signal, the radio signal including a firstfrequency band including a first signal, the first signal including aplurality of TDD-frames; wherein the receiver is configured to evaluatereception of downlink data to obtain evaluation data; wherein thereceiver is configured to transmit the evaluation data in a secondfrequency band outside the first frequency band.

Another embodiment may have a receiver, wherein the receiver isconfigured to receive and process a radio signal, the radio signalincluding a first frequency band including a first signal, the firstsignal including a plurality of TDD-frames; wherein the receiver isconfigured to transmit data in a second frequency band outside the firstfrequency band during a downlink-only subframe of a TDD-frame of theplurality of TDD-frames.

Another embodiment may have a transmitter, wherein the transmitter isconfigured to receive and process a radio signal, the radio signalincluding a first frequency band including a first signal, the firstsignal including a plurality of TDD-frames; wherein the transmitter isconfigured to evaluate reception of downlink data to obtain evaluationdata; wherein the transmitter is configured to transmit the evaluationdata in a second frequency band outside the first frequency band.

According to another embodiment, a radio signal may have: evaluationdata relating to an evaluation of a reception of data received during aTDD-frame of a first signal in a first frequency band, wherein the radiosignal includes a second frequency band and is transmitted during aTDD-frame of the radio signal.

According to another embodiment, a wireless communication system mayhave: an inventive receiver or a receiver, wherein the receiver isconfigured to receive and process a radio signal, the radio signalincluding a first frequency band including a first signal, the firstsignal including a plurality of TDD-frames; wherein the receiver isconfigured to transmit data in a second frequency band outside the firstfrequency band during a downlink-only subframe of a TDD-frame of theplurality of TDD-frames; and a transmitter wherein the transmitter isconfigured to receive and process a radio signal, the radio signalincluding a first frequency band including a first signal, the firstsignal including a plurality of TDD-frames; wherein the transmitter isconfigured to evaluate reception of downlink data to obtain evaluationdata; wherein the transmitter is configured to transmit the evaluationdata in a second frequency band outside the first frequency band.

According to another embodiment, a method may have the steps of:receiving and processing a radio signal, the radio signal including afirst frequency band including a first signal, the first signalincluding a plurality of TDD-frames; evaluating reception of downlinkdata to obtain evaluation data; transmitting the evaluation data in asecond frequency band outside the first frequency band.

According to another embodiment, a method may have the steps of:receiving and processing a radio signal, the radio signal including afirst frequency band including a first signal, the first signalincluding a plurality of TDD-frames; transmitting data in a secondfrequency band outside the first frequency band during a downlink-onlysubframe of a TDD-frame of the plurality of TDD-frames.

Another embodiment may have a non-transitory digital storage mediumhaving a computer program stored thereon to perform a method, the methodhaving the steps of: receiving and processing a radio signal, the radiosignal including a first frequency band including a first signal, thefirst signal including a plurality of TDD-frames; evaluating receptionof downlink data to obtain evaluation data; transmitting the evaluationdata in a second frequency band outside the first frequency band, whensaid computer program is run by a computer.

Another embodiment may have a non-transitory digital storage mediumhaving a computer program stored thereon to perform a method, the methodhaving the steps of: receiving and processing a radio signal, the radiosignal including a first frequency band including a first signal, thefirst signal including a plurality of TDD-frames; transmitting data in asecond frequency band outside the first frequency band during adownlink-only subframe of a TDD-frame of the plurality of TDD-frames,when said computer program is run by a computer.

The inventors have found out that data such as evaluation data, but alsouser data or control information may be transmitted in a TDD scheme froma receiving node during reception or during downlink phases of thecommunication when using a communication channel being arranged in asecond frequency band unused by the first frequency band used for thetransmission of the download data. This allows for transmission by thereceiving node even when no transmission is scheduled in the firstfrequency band in the TDD scheme.

According to an embodiment a receiver is provided, wherein the receiveris configured to receive and process a radio signal. The radio signalcomprises a first frequency band including a first signal, the firstsignal comprising a plurality of TDD-frames. The receiver is configuredto evaluate reception of a downlink data to obtain evaluation data. Thereceiver is further configured to transmit the evaluation data in asecond frequency band outside of the first frequency band. This allowsto transmit the evaluation data, for example indicating an ACK or NACK,to be transmitted previously to the earliest uplink frame scheduled tothe receiver and thus to transmit the ACK and/or NACK with a low delayso as to inform the transmitter of the downlink data at an early stageof data processing.

According to embodiments each TDD-frame comprises a plurality ofsubframes. Those subframes may be defined as uplink-only subframe or asa downlink-only subframe. The receiver may be configured to transmit theevaluation data during a downlink subframe. For example, the receivermay be configured to transmit the evaluation data in an uplink subframeof an NB-IoT frame. The NB-IoT frame may be arranged in an LTE carrier(in-band) in a guard band of the LTE carrier or in a GSM carrier as wellas any other frequency bands. This allows using a narrow bandwidth ofthe NB-IoT bandwidth to transmit this relatively small amount ofinformation when compared to the amount of downlink data. Althoughcomprising a narrow bandwidth a NB-IoT frame may comprise sufficientthroughput and may usually be acquired by a low amount of IoT devices,thus providing unused bandwidth.

Further embodiments provide a receiver being configured to transmit theevaluation data in at least a first uplink channel and a second uplinkchannel, the first uplink channel and the second uplink channel eachcomprising a bandwidth being narrower when compared to a bandwidth ofthe first frequency band. The receiver may thus use a further uplinkchannel in combination with the second frequency band so as to increaseuplink bandwidth which may allow for an at least statistically low delaywhen having the possibility to access at least two uplink channels. Thereceiver may be configured to aggregate the first and second uplinkchannel and may apply a common channel code to the first uplink channeland the second uplink channel so as to define a virtual channelcomprising a higher bandwidth when compared to the second frequencyband. For example, different NB-IoT frames being arranged in differentfrequency bands may be used.

Further embodiments provide a receiver being configured to determine aprediction value indicating a likelihood of error-free coding of thedownlink data. This may allow determining the prediction value duringprocessing of the received downlink data, i.e., before reception and/orprocessing of the downlink data is complete. The receiver may include apositive acknowledgement (ACK) into the evaluation data when thelikelihood is above a threshold value and to include a negativeacknowledgement (NACK) into the evaluation data when the likelihood isbelow the threshold value. Thus, evaluation data indicating successfulreception, error-prone reception respectively may be formed beforereception or decoding of the downlink data is completed. This allows thereceiver to transmit the evaluation data indicating a successfuldecoding or indicating a requirement for retransmission before thetransmitter of the downlink data has completed its actual attempt oftransmitting data and thus allows for a low delay between transmissionand ACK/NACK.

According to a further embodiment the receiver is configured to includefurther information into the evaluation data. The further informationmay be an information indicating an amount of additional redundancy forretransmission, the additional redundancy allowing for probablyerror-free reception of the downlink data in retransmission, informationindicating one of a frequency, a time, a frame or a slot within a framefor retransmission, i.e., the receiver may include a location indicatorwhich may be understood as a suggestion on retransmission resources forthe transmitter, which may be based on perceived channel quality at thereceiver. The receiver may alternatively or additionally includeinformation relating to a channel quality determined by the receiverand/or information related to a code block of the downlink data, i.e.,if a transmission block is derived of several code blocks in thecommunication scheme, the code block for retransmission may beindicated. Including such information into the evaluation data may allowfor supporting the transmitter to find suitable parameters forretransmission which on the one hand allow for a presumably error-freetransmission of the downlink data, a low amount of attempts forretransmission and to save resources during retransmission, for example,when avoiding usage of unneeded additional redundancy.

Further embodiments provide a receiver, wherein the receiver isconfigured to receive and process a radio signal, the radio signalcomprising a first frequency band including a first signal, the firstsignal comprising a plurality of TDD-frames. The receiver is configuredto transmit data in a second frequency band outside of the firstfrequency band during a downlink-only subframe of a TDD-frame of theplurality of TDD-frames. This may allow transmitting data in the secondfrequency band although the receiver is unable to currently transmit inthe first frequency band due to the present downlink-only subframe. Thedata transmitted in the second frequency band may be, for example, userdata, control data or evaluation data. This may allow the receiver totransmit data although it would have to wait for transmission in the TDDscheme and may thus allow for a short delay in data exchange.

Further embodiments provide a transmitter, wherein the transmitter isconfigured to receive and process a radio signal, the radio signalcomprising a first frequency band including a first signal, the firstsignal comprising a plurality of TDD-frames. The transmitter isconfigured to evaluate reception of downlink data to obtain evaluationdata. The transmitter is configured to transmit the evaluation data in asecond frequency band outside of the first frequency band. Thetransmitter may be, for example, an eNB (evolved node B, i.e., a basestation). By using the second frequency band, reception of data uploadedby another node of the communication networks, for example, a receiveraccording to the teachings disclosed herein, may be acknowledged.

Further embodiments provide a radio signal comprising evaluation datarelating to an evaluation of a reception of data received during aTDD-frame of a first signal in a first frequency band. The radio signalcomprises a second frequency band and is transmitted during a TDD-frameof a radio signal.

Further embodiments provide a wireless communication system comprising areceiver according to the teachings disclosed herein and a transmitteraccording to the teachings disclosed herein.

Further embodiments provide a method. The method comprises receiving andprocessing a radio signal, the radio signal comprising a first frequencyband including a first signal, the first signal comprising a pluralityof TDD-frames. The method comprises evaluating reception of downlinkdata to obtain evaluation data and transmitting the evaluation data in asecond frequency band outside the first frequency band.

Further embodiments provide a method comprising receiving and processinga radio signal, the radio signal comprising a first frequency bandincluding a first signal, the first signal comprising a plurality ofTDD-frames. The method further comprises transmitting data in a secondfrequency band outside the first frequency band during a downlink-onlysubframe of a TDD-frame of the plurality of TDD-frames.

Further embodiments provide a non-transitory computer program productcomprising a computer-readable medium storing instructions which, whenexecuted on a computer, perform a method according to the teachingsdisclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 is a schematic representation of an example of a networkinfrastructure;

FIG. 2 is schematic representation of an exemplary LTE OFDMA-basedsubframe with two antenna ports for different selected Tx antenna ports;

FIG. 3 a is a schematic representation of a scenario in which an LTE aframe comprise TDD resources;

FIG. 3 b is a schematic representation of possible uplink/downlinkconfigurations in the scenario of FIG. 3 a;

FIG. 4 is a schematic table illustrating a timing of HARQ responses fordifferent UL/DL configurations in LTE;

FIG. 5 is a schematic representation of an example of how PHICHs may bemapped to resources, wherein three PHICH groups are shown;

FIG. 6 is a schematic representation of a number of PHICH groups with 10MHz channel bandwidth;

FIG. 7 is a tabular describing parts of the specification described in3GPP specification;

FIG. 8 is another tabular format of description of specification toillustrate the contents of ARQ and CSI;

FIG. 9 shows a schematic block diagram of a receiver according to anembodiment;

FIG. 10 shows a schematic diagram illustrating a possible timing whenimplementing a fast transmission of an ACK/NACK response according to anembodiment;

FIG. 11 a shows the arrangement of an NB-IoT carrier in-band LTEaccording to an embodiment;

FIG. 11 b shows the arrangement of an NB-IoT carrier in a stand-aloneGSM operation mode according to an embodiment;

FIG. 11 c shows the arrangement of an NB-IoT carrier in an LTE guardband according to an embodiment;

FIG. 12 illustrates a schematic diagram of a possible channel accesswhich may be performed by the receiver according to an embodiment;

FIG. 13 is a schematic diagram of a timing of sequences modulated on thetransmission in the NB-side channel, according to an embodiment;

FIG. 14 shows a schematic block diagram of a transmitter according to anembodiment;

FIG. 15 illustrates a schematic diagram of a communications networkaccording to an embodiment;

FIG. 16 illustrates a set of pseudo code which may be used forimplementing embodiments described herein;

FIG. 17 shows a schematic flow diagram of a method for transmittingevaluation data, according to an embodiment; and

FIG. 18 shows a schematic flowchart of a method for transmitting data,according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

In the following, embodiments of the present invention are described infurther detail with reference to the enclosed drawings in which elementshaving the same or a similar function are referenced by the samereference signs.

Some embodiments described hereinafter relate to a receiver. Someembodiments relate to a transmitter. A receiver may be understood as areceiving node of a communications system that is scheduled to receiveor at least to not transmit data during a downlink frame or a downlinksubframe of a TDD scheme. A transmitter may be understood as atransmitting node of the communications system that is scheduled totransmit data during the downlink frame or subframe. In a differentframe or subframe such as an uplink subframe, the receiver or adifferent receiver may be configured to transmit data, wherein thetransmitter is configured to receive the data. Thus, the functionalitydescribed herein for receivers and for transmitters may beinterchangeable according to a downlink or uplink frame or subframe.Downlink hereinafter relates to a transmission from a transmitter suchas a base station to a receiver such as a UE, wherein uplink relates toa transmission from a receiver (related to the downlink phase) to thetransmitter (related to the downlink phase).

FIG. 9 shows a schematic block diagram of a receiver 110. The receivercomprises an antenna 112 a and is configured to receive and process aradio signal 114 with the antenna 112 a. The radio signal 114 comprisesa first frequency band f₁ including a first signal. The first signal maybe mobile communications signal such as an LTE signal or a GSM signal. Abandwidth of the frequency band f₁ may be, for example, 1.4 MHz or more.The first signal comprises a plurality of TDD-frames. The receiver 110is configured to evaluate reception of downlink data contained in thefirst signal so as to obtain evaluation data. The receiver may comprisea processor 116 for evaluating the reception of downlink data theprocessor 110. The processor 116 may be configured to decode the firstsignal. During or after decoding of the first signal the processor 116may determine a quality of the transmission of the downlink data. Thismay include, among other things, a number of bit errors, a phase-shiftof the received signal and/or a signal-to-noise-ratio.

The receiver 110 is configured to obtain evaluation data, for example,it may generate evaluation data with the processor 116. The evaluationdata may comprise, among other things, a feedback to the transmitter ofthe signal 114 indicating a successful or unsuccessful reception, forexample, by including an ACK or a NACK message into the evaluation data,e.g. in a HARQ process.

The receiver is configured to access a second frequency band f₂ and totransmit messages on that second frequency band f₂ via a radio signal118. The second frequency band f₂ may comprise a second signal. Thesecond signal may comprise a plurality of TDD-frames. For example, someof the subframes of the TDD-frame may be uplink—only subframes ordownlink-only subframes. According to other examples, the TDD-frames maybe uplink-only or downlink-only. According to other examples, the secondfrequency band may be accessed via an FDD-scheme. The receiver may beconfigured to use the first frequency band f₁ which is used for a firstmobile communication standard, wherein the second frequency band f₂ isused for a second mobile communication standard.

The receiver may access the second frequency band f₂ during a downlinkframe or subframe of a TDD-frame is scheduled in the communicationbetween the receiver 110 and a transmitter.

The receiver 116 is configured to transmit information such as theevaluation data in the second frequency band f₂. The second frequencyband f₂ is arranged outside the first frequency band f₁. As will bedescribed in connection with FIGS. 11 a to 11 c in more detail, thesecond frequency band f₂ being arranged outside the first frequency bandf₁ may be understood as the frequency band f₂ being a frequency range orfrequency band which is unoccupied by the signal 114 for transmission ofthe downlink data. Thus, the frequency band f₂ may be arranged at leastpartially out-of-band at a frequency band lower than a lowest frequencyof the frequency band f₁, higher than a highest frequency of thefrequency band f₁ and/or may be arranged in-band at a frequency regionbetween a lowest frequency and a highest frequency of the frequency bandf₁, i.e., the second frequency band being outside the first frequencyband does not necessarily mean that the frequency band f₂ is separatedfrom the frequency band f₁.

Although the receiver 110 is illustrated as comprising two antennas 112a and 112 b, one for uplink and downlink, the receiver 110 may comprisea different number of antennas. For example, the receiver 110 maycomprise only one antenna configured for transmission and reception.Alternatively, the receiver 110 may comprise a number of antennas beinggreater than 2, for example, for assessing different frequency bandswith different antennas. The receiver may be, for example, a UE such asa mobile phone, a tablet computer or any other communication node.

FIG. 10 shows a schematic diagram illustrating a possible timing whenimplementing a fast transmission of an ACK/NACK response. The scenariomay be identical to the one explained in connection with FIG. 3 , i.e.,eNB transmits downlink data in subframe 202 ₅ of frame N. Thetransmission is disturbed, i.e., error-prone such that retransmission isneeded. As soon as the UE (receiver) evaluates the reception of thedownlink data and detects that a retransmission is needed, it maytransmit the evaluation data in the second frequency band f₂ using thesignal 118. This may be, for example, during the frame 202 ₆, which maybe, for example, a downlink-only subframe in the frequency band f₁.

When using the second frequency band f₂ for transmitting the evaluationdata a timing of transmission of the evaluation data may be different oreven independent from a timing of the frames and/or subframes of theradio signal 114. As will be described later in more detail, the secondfrequency band f₂ may be used for a different communications protocol.for example, the second frequency band f₂ may be a GSM carrier, whereinthe first frequency band f₁ may be an LTE frequency band. When accessinga GSM carrier for transmitting the evaluation data while receivingdownlink data via an LTE carrier the signal 118 may be adapted to a GSMtiming or the like, wherein the downlink data is received according toan LTE timing. After reception of the evaluation data by the eNB aretransmission of the downlink data may be performed by the transmitter.According to one scenario, this may be the next downlink frame followingthe reception of the evaluation data. Thus, although the receiver 110,the UE respectively may be trapped in a downlink-only phase of frame Nand/or in a subframe which does not allow transmission of own messageslike subframe 202 ₁. The UE may transmit its response, i.e., theevaluation data and therefore may signalize the request forretransmission earlier when compared to the scenario of FIG. 3 .

Bars 122 indicate times during which the UE is usually not provided withuplink capacity for data exchange in the frames N and/or N+1 are. Thus,during subframes indicated by the bars 122 a delay may be caused bywaiting for uplink capacity and thus for retransmitting ACK and/or NACKin the first frequency band f₁. By using the second frequency band f₂,this delay may at least be reduced.

According to one example, the receiver 110 is configured to transmit theevaluation data in frequency band 1, for example, in uplink subframes202 ₂, 202 ₃ and/or 202 ₄, when such a frame is following a downlinkframe or at least following a disturbed transmission with a low delay.For example, when the signal 114 is transmitted in downlink-onlysubframe 202 ₀, the receiver 110 may be configured to transmit theevaluation data in uplink-only subframe 202 ₂ using frequency band f₁according to a regular network configuration. According to anotherexample, receiver 110 may be configured to use frequency band f₂.According to another example, the receiver 110 may be configured toapply further decision parameters. For example, the receiver 110 mayevaluate a probability of being allocated uplink resources in the nextuplink frame. When it is unlikely to be allowed to transmit evaluationdata in the next uplink subframe or when the receiver has to wait longerthan a time threshold, then the receiver 110 may be configured to decideto use frequency band f₂. A time threshold may be any applicable value,for example, 1 subframe, 2 subframes or 3 subframes.

In other words, FIGS. 3 and 10 show a transmission of downlink data insubframe 5. When no narrow band (NB) channel is used for fasttransmission of an ACK/NACK the response can be sent the earliest in thenext uplink frame, i.e., frame 202 ₂, as illustrated in FIG. 3 . Thiscan trigger a retransmission earliest in the next downlink subframe,i.e., subframe 5. When using a NB HARQ UL channel, i.e., the frequencyband f₂, the ACK/NACK can be sent earlier or even immediately and aretransmission may also be triggered earlier, in this case in subframe8. The NB-UL channel may be an NB-IoT channel, where some UL resourcesare reserved for LTE/5G PUCCH.

According to examples, the second frequency band f₂ is at least part ofa frequency band designated for NB-IoT. Three operating modes for NB-IoTare now described with reference to FIGS. 11 a to 11 c , namely thein-band LTE operation mode (FIG. 11 a ), the stand-alone GSM operationmode (FIG. 11 b ) and the LTE guard band operation mode (FIG. 11 c ).FIGS. 11 a to 11 c are schematic representations of different operatingmodes in accordance with NB-IoT, also referred to as the NB-IoT. Thus,the receiver may be configured to operate in accordance with the LTEstandard, whereas the second frequency band may comprise an NB-IoTchannel.

FIG. 11 a shows the in-band LTE operation mode in accordance with whicha NB-IoT carrier or frequency band 300, also referred to as NB-IoTchannel, is deployed within the LTE carrier of frequency band 301. TheLTE frequency band 301 may correspond to the first frequency band f₁.The NB-IoT carrier of frequency band 300 may be used as second frequencyband f₂.

FIG. 11 b shows the stand-alone GSM operation mode placing the NB-IoTfrequency band 300 among a plurality of GSM carriers 302. The NB-IoTfrequency band 300 may be separated by a guard band from the GSMcarriers. The GSM carriers 302 may be used as first frequency band f₁.

FIG. 11 c shows the LTE guard band operation mode in accordance withwhich the NB-IoT carrier 300 is placed in one of the LTE guard bandsprovided at both ends of the carrier of the standard LTE.

Although FIGS. 11 a to 11 c illustrate the second frequency band f₂being arranged inside or adjacent to a frequency interval between aminimum frequency and a maximum frequency of the frequency band f₁, theabove-described and non-limiting scenarios are combinable with eachother. The second frequency band f₂ may be any frequency band unused bythe frequency band 301 or 302. For example, a receiver may receive thefirst signal in the first frequency band f₁ illustrated in FIG. 11 a or11 c while using the second frequency range f₂ for transmitting theevaluation data as illustrated in FIG. 11 b or vice versa. Alternativelyor in addition, further or other frequency bands may be used for thefirst frequency band f₁ and/or the second frequency band f₂. In otherwords, in LTE REL. 13, NB-IoT channels in the LTE assistance can beeither embedded in-band, or in the guard band of an existing LTEcarrier. A basic narrowband (NB) carrier uses, for example, 200 kHzbandwidth or one Physical Resource Block (PRB)=12 subcarriers infrequency domain. Such an NB carrier may provide enough bandwidth fortransmitting data such as the evaluation data comprising data relatingto HARQ ACK or NACK. It is noted, that the second frequency band is notlimited to utilization of NB-IoT carriers and/or that NB-IoT carriersmay exist or may be defined with other properties than described hereinwithout limiting the examples described herein to the presentembodiments. When the receiver uses an NB-IoT frame for transmitting theevaluation data in the second frequency band, the receiver may beconfigured to transmit the evaluation data during an uplink subframe ofan NB-IoT frame, i.e., the receiver may be configured to communicateaccording to the respective protocol used in the second frequency band.

FIG. 12 illustrates a schematic diagram of a possible channel accesswhich may be performed by the receiver 110, for example. A plurality ofsubframes 202 ₂ to 202 ₈ are schematically presented. For illustrationpurpose only the subframes each comprise a downlink-only configurationincluding resources for signaling such as primary synchronizationsignals (PSS) and/or secondary synchronization signals (SSS). An examplebandwidth of the first frequency band f₁ may be between 1.4 MHz and 20MHz. The receiver may access the second frequency band f₂ comprising abandwidth BM. As was described with reference to FIGS. 11 a to 11 c ,the frequency band f₂ may be, for example, an NB-IoT carrier 300.Simplified, the receiver may use the bandwidth of the second frequencyband f₂ of the NB-IoT carrier 300 a. Additionally, the receiver may usea further frequency band f₃ comprising a further bandwidth BW₂ which maybe, for example, a further NB-IoT carrier 302 b. A receiver according toembodiments described herein may be configured to use two or even morethan two frequency bands outside of the frequency band f₁ as ARQ/HARQchannel. Simplified, the receiver may use two or more NB-IoT carriers,i.e., a 2^(nd) a 3^(rd), . . . , an n^(th) carrier probably aggregatedchannel in frequency domain. For example, the receiver may be configuredto use a frequency band fa associated to an NB-IoT in Guard Bandalternatively to frequency band f₂ and/or f₃ or in addition hereto.

For example, the receiver may decide to use one of the carriers 300 a or300 b (or a different carrier) for transmitting the evaluation data,e.g., based on a workload of the respective channel. Alternatively, thereceiver may be configured to use both carriers 300 a and 300 b at thesame time, i.e., to combine the frequency bands f₂ and f₃. The frequencybands f₂ and f₃ may be adjacent to each other or may be separated fromeach other in the frequency domain. Thus, the second frequency band mayalso be a combination of several NB-IoT channels, e.g., a combination oftwo or more NB-IoT channels in the guard band, of two or more in-bandNB-IoT channels and/or two or more guard band NB-IoT channels and/or acombination of different types of NB-IoT channels. A type of combinationmay differ between different receivers and may be influenced or maydepend on the operating mode of the communication system. As wasdescribed with reference to FIG. 11 a to FIG. 11 c one or more NB-IoTchannels may be located in other bands different from the firstfrequency band, such as GSM carriers. In other words, 1, 2, . . . N_SCnarrowband carriers may be used as separate ARQ/HARQ channel, whereinN_SC may be any value, e.g. less than 1,000, less than 500 or less than100. Each carrier used may be in-band and/or in the guard-band of anexisting LTE carrier and/or in other carriers. If a higher bandwidthwhen compared to one single narrowband carrier is needed, several NBbands may be aggregated. The robustness of this special HARQ band may beincreased or may be high by using a channel code over the N aggregatedHARQ channels. Note that N may be one, two or a higher number such asthree, four, five or more.

In other words, the inner 1.4 MHz of the LTE band is reserved formandatory LTE control channels such as synchronization signals (PSS/SSS)and broadcast information (PBCH). These frequency bands maybe cannot beused for NB-IoT subchannels. Also non-continuous NB-IoT could be bundledinto a logical NB-IoT HARQ channel, e.g. the channels at frequency bandsf₂ and fa. Alternatively or in addition, the receiver may be configuredto reuse this “HARQ Channel”, i.e. at least one frequency band, asseparate data channel for higher layers, e.g. transport layer. Sincethis channel has low capacity, small packets from a higher layer (whichare not piggybacked) may be mapped onto this channel. This enables afaster transport of small packets. If more NB-IoT channels areaggregated, channel coding with interleaving across the aggregated bandswill improve the robustness of transmission by better exploit frequencydiversity and thus improve overall efficiency.

Thus, the receiver may be configured to transmit the evaluation data inat least a first uplink channel and a second uplink channel, the firstuplink channel and the second uplink channel each comprising a bandwidthbeing narrower when compared to a bandwidth of the first frequency band.The receiver may be configured to aggregate the first uplink channel andthe second uplink channel by applying a common channel code to the firstuplink channel and to the second uplink channel, for example whenutilizing adjacent frequency bands such as f₂ and f₃. This may allow forincreasing capacity in this feedback channel and may increase robustnesssince coding and interleaving can be utilized over a wider bandwidth.Coding and interleaving may be executed by the receiver for adjacent andfor separated channels such as f₂ and f₄ and/or f₃ and f₄.Alternatively, both channels could multiplex the same HARQ information,and the decoder on the receive side could perform HARQ channelselection, to increase robustness.

When referring again to FIG. 10 , a possible configuration of thereceiver 110 shall be explained. When receiving the transmitted downloaddata with the signal 114, the processor may process and/or decode thereceived data portion by portion, for example, symbol-by-symbol,bit-by-bit or byte-by-byte or the like. Thus, although receiving apossibly large amount of data, this data is processed step-by-step.According to one example, the receiver buffers all data received andtries to decode it when reception is complete, wherein it may determinethat decoding is not possible or the quality is below a threshold value.According to further embodiment, the receiver is configured to determinea prediction value indicating a likelihood of error-free decoding of thedownlink data during this step-wise processing, i.e., before receptionis complete. Error-free means a number of errors which is still be to becorrected by the receiver. This may also be referred to asonline-evaluation. For example, based on parameters like phase-shiftsand/or inclined signal edges, the receiver may determine that it is verylikely that bit-errors will occur. The receiver may also evaluate ordetermine that an amount of bit-errors may be critical for error-freedecoding or may determine that channel malfunctions are increasingduring reception. Simplified, the receiver may monitor or determine if apacket received may be decoded correctly after reception but also duringreception. During reception the receiver may determine a prediction onhow likely the packet may be decoded when it is finally received. Thus,the receiver may determine a prediction value indicating a likelihood oferror-free decoding of the downlink data. The receiver may include apositive acknowledgement into the evaluation data when the likelihood isabove a threshold value and to include a negative acknowledgement intothe evaluation data when the likelihood is below the threshold value.Thus, the receiver may transmit evaluation data based on a predictionrelating to a successful reception. In other words, a predictive HARQmay be sent back to the transmitter.

When still referring to FIG. 10 , the NACK may be sent during a timeduration of the subframe 202 ₅, when the receiver determines that it islikely to not decode the received data correctly. Thus, the receiver maybe configured to transmit the evaluation data before processing of thereceived downlink data is complete. The likelihood threshold value maybe of any suitable value, for example, at least 90%, at least 95% or atleast 99% probability of successful decoding. Although being describedas a likelihood value for successful decoding, embodiments shall not belimited thereto. It is also possible to determine a threshold valueindicating a likelihood or probability of disturbed or unsuccessfuldecoding, wherein the processor may transmit a NACK-message in theevaluation data when the determined likelihood is above the thresholdvalue. For example, the threshold value may be at most 10%, at most 5%or at most 1% probability of erroneous decoding. Further, it is notneeded to directly determine the likelihood. Any other parameters suchas a bit-error count or a phase-shift variation during reception may beused as indicating value and thus for determining, if a positiveacknowledgement (ACK) or a negative acknowledgement (NACK) should betransmitted.

Independent from a time at which the receiver transmits the evaluationdata, further information can be added to the HARQ. Further informationcan be, for example, a redundancy indicator indicating how muchredundancy is missing or shall be spent by the transmitter to allow fora successful decoding. Alternatively or in addition, the evaluation datamay comprise a location indicator which may be a suggestion onretransmission resources and may be based on a perceived channel qualityat the receiver. Alternatively or in addition, a Channel QualityIndicator (CQI) may be included into or added to the evaluation data toassist retransmission scheduling at the transmitter. Thus, the receivermay indicate which channels may be suitable for retransmission.Alternatively or in addition, the evaluation data may further comprise aCode Block Indicator (CBI). If a transmission block is derived ofseveral code blocks, the code block suggested for retransmission may beindicated. Alternatively or in addition, the receiver may be configuredto predict a decoding probability if the additional redundancy wasspent. The evaluation data may comprise information relating to thisdecoding probability.

Each of the aforementioned information may also be transmitted duringreception or after reception of the retransmission. Beside the shorterdelay between transmission and retransmission such information may allowfor changing a coding of the data transmitted. This may allow forpreventing unsuccessful decoding such that a retransmission may beunnecessary.

As alternative to or in addition to the evaluation data, the receiver110 may be configured to transmit control data related to a resourceallocation of the first signal in the first frequency f₁ band and/or totransmit user data. Simplified, the receiver may use the bandwidth ofone or more narrowband side channels to transmit the evaluation data andfurther information such as control data or user data. Control data mayindicate a position of the evaluation data or other data in the secondsignal in the time domain and/or in the frequency domain. The receivermay also be configured to receive such a control data and to transmitthe evaluation data or the data at the indicated position in the secondsignal. Thus, the control data may indicate a control over anothercommunication partner or may comprise user data of the receiver. Controldata of another communication partner may be, for example, beinformation indicating an amount of additional redundancy forretransmission, information indicating one of a frequency, a time, aframe or a slot within a frame for retransmission, information relatingto a channel quality determined by the receiver, information related toa code block of the downlink data and/or a decoding probability forrequested additional redundancy. In other words, when using a TDD systemand other UL is probably unavailable, this channel may additionally beused for other control data for user data, e.g. to better supportlatency constrained traffic and to reuse additional latency or jittercoming from a blocked ACK or NACK.

The additional information may contain other control channels such asMIMO feedback information, for example, channel quality information(CQI) Channel state information (CSI), pre-coding matrix indicator (PMI)or rank indicator (RI) for a particular subband or group of subbands.This information may include incremental feedback information. Inaddition, this channel may carry user data as well.

The receiver 110 may be configured to include a scheduling request intothe evaluation data. The scheduling request may relate to a request foruplink resources in a TDD-frame. For example, the TDD-frame may comprisea plurality of subframes, wherein a subframe of the plurality ofsubframes is an uplink-only subframe or a downlink-only subframe. Thereceiver may be configured to include, into the evaluation data, thescheduling request or the request for using an uplink-only subframe.This may allow achieving lower uplink transmission latency by indicatinga scheduling request during TDD downlink transmission using the NB-sidechannel, i.e., the second frequency band f₂. This may bring significantgains in UL transmission latency in TDD systems.

As illustrated in FIG. 13 , sequences may be modulated on thetransmission in the NB-side channel. The receiver is configured totransmit the evaluation data, the scheduling request (SR) respectively,such that a user identification, i.e., an identification of the receiveris possible at the eNB side, for example, by inserting an identifier orthe like. Additionally, buffer status or expected UL transmission sizemay be indicated by the receiver. As explained in connection with FIGS.11 a to 11 c , the evaluation data may be transmitted, for example in aguard band of the LTE carrier and/or in a physical scheduling requestuplink channel (PSRUCH).

Alternatively or in addition, the second frequency band f₂ may be usedfor other data than evaluation data such as a physical upload controlchannel (PUCCH). Based on the low bandwidth it is referred tohereinafter as NB PUCCH channel. The position of the NB PUCCH channelmay be signaled by the receiver. This may be done at the user equipment(receiver), e.g., over RRC or as part of the system information. Usersmay be implicitly assigned resources depending on the resourceassignment they should report on. Alternatively or in addition, usersmay receive a PUCCH slot as part of the DCI. For semi-persistentscheduling (SPS) a longer term assignment may be set. Alternatively,users may be multiplexed using codes such as Gold, DFT, Hadamard or thelike. The codes may be spread among the time and/or frequency resources.Both sides have to agree on which codes and sequence should be used on atransmitter and receiver side.

Each of the aforementioned data to be transmitted from the receiver tothe transmitter (or other nodes) may be implemented independently fromeach other and may be combined with each other in an arbitrary way. Thereceiver 110 may be configured to receive and process a radio signal,the radio signal comprising a first frequency band including a firstsignal, the first signal comprising a plurality of TDD-frames. Thereceiver is configured to transmit data in the second frequency bandoutside of the first frequency band during a downlink-only subframe of aTDD-frame of the plurality of TDD-frames. The data transmitted in thesecond frequency band may be the ACK/NACK evaluation data, control dataand/or user data including the scheduling requests and/or signalingdata, for example, relating to the position of the PUCCH channel and/ora combination thereof.

FIG. 14 shows a schematic block diagram of a transmitter 410. Thetransmitter 410 comprises a similar functionality when compared to thereceiver 110, for example during an uplink frame or subframe. Thereceiver 410 comprises the antennas 412 a and/or 412 b for receiving thefirst frequency band f₁ and for transmitting in the second frequencyband f₂. The antennas 412 a and 412 b may correspond to the antennas 112a and 112 b. The transmitter 410 comprises the processor 416 which maycorrespond to the processor 116. The transmitter is configured toreceive and process the radio signal 114, and the radio signal comprisesthe first frequency band f₁ including a first signal, the first signalcomprising a plurality of TDD-frames. The transmitter may be configuredto transmit data in the second frequency band outside of the firstfrequency band during an uplink-only subframe of a TDD-frame of aplurality of TDD-frames. The transmitter is configured to evaluatereception of downlink data to obtain evaluation data. The transmitter410 is further configured to transmit the evaluation data in the secondfrequency band f₂ outside of the first frequency band f₁. Simplified,TDD-frames may comprise uplink and downlink sequences, wherein, whenswitching from a downlink sequence (reception of the signal in the firstfrequency band f₁ by the receiver 110) to an uplink sequence (receptionof the signal in the first frequency band f₁ by the transmitter 410).The same mechanisms may be used to enhance communication between bothnodes, the receiver 110 and the transmitter 410.

In accordance with the functionality of the transmitter, a receiver suchas the receiver 110 may be configured to receive evaluation data in thesecond frequency band f₂ which is transmitted responsive to atransmission of data in the first frequency band f₁ by the receiver. Inother words, the NB channel may be used for HARQ from eNB for UE uplinktransmissions.

The transmitter 410 may be configured to operate as an eNB which is a 3Gbase station. The transmitter 410 may be configured to transmit scheduledata indicating a schedule of a NB-IoT node such as the NB-IoT node 104₂ transmitting in the second frequency band such as a sensor, a buildingor the like. The transmitter 410 may be configured to generate theschedule data so as to schedule the transmission of the NB-IoT node toan uplink subframe of the second signal in the second frequency band f₂,wherein the uplink subframe to which the resources are scheduled may beunused for a transmission by the transmitter or a user equipment(receiver 110) communicating with the transmitter 410 in the firstfrequency band f₁. Simplified, the transmitter 410 may organize theschedule of the second frequency band by not scheduling NB-IoT deviceson the resources used by the receiver or transmitter for a side-channelcommunication, for example, for PUCCH. This may allow for a co-existencebetween the NB-IoT devices and the side-channel communication. The datareceived by the transmitter 410 may comprise a control data indicating acontrol of another communication partner or may comprise user data of areceiver as described with reference to the receiver.

FIG. 15 illustrates a schematic diagram of a communications network 500comprising a receiver, for example, the receiver 110 and comprising atransmitter, for example, the transmitter 410. The receiver 110transmits, in the second frequency band f₂, a radio signal 510, forexample, the radio signal 118. The radio signal 510 comprises evaluationdata relating to an evaluation of a reception of data received during aTDD-frame of the first signal 114 in the first frequency band f₁. Theradio signal 510 comprises the second frequency band f₂ and istransmitted during a TDD-frame of the radio signal 114.

FIG. 16 illustrates a set of pseudo code which may be used forimplementing examples described herein. For example, a separate physicalHARQ indicator channel (PHICH) may be implemented or run on a NBdownload band. This may additionally be signaled in the masterinformation block (MIB) of the LTE protocol. The pseudo code comprisesthree blocks 610, 620 and 630. Although the last line of the code block630 indicates that only one channel C1, C2, . . . , CN is used,alternatively two or more channels may be assigned, for example, forusing frequency diversity. This may be in accordance as done for PUCCHUL transmissions at both sides for the PUSCH. The pseudo code block 610describes the content of the Master Information Block (MIB).

In block 620 an optional narrowband Physical HARQ Indicator Channel(NB-PHICH) is added as indicated by the code

-   -   nb-phich-Config NB-PHICH-Config OPTIONAL,-Need ON.

Code Block 630 is one possible example which describes the content ofthe nb-phich-Config

NB-PHICH-Config ::= SEQUENCE { phich-Duration ENUMERATED {normal,extended}, phich-Resource ENUMERATED {oneSixth, half, one, two}phich-Location ENUMERATED {c1, c2, ..., cN} }

By the above code as an example some parameters of the narrowband PHICHare defined such as the duration, resources to use and the location ofthe channel. For using, as an non-limiting example only, frequencydiversity by utilizing at least two NB-IoT channels, phich-Location mayrefer to a position of the one or more of the additional frequency bandsin the frequency domain, for example, the frequency bands f₂, f₃, and/orf₄ in FIG. 12 .

Alternatively, the functionality of the pseudo code may be obtained bysimilarly configuring the network on a UE basis over RRC.

FIG. 17 shows a schematic flow diagram of a method 700. The method 700comprises a step 710 in which a radio signal is received and processed.The radio signal comprises a first frequency band such as the frequencyband f₁ including a first signal, the first signal comprising aplurality of TDD-frames. A step 720 comprises evaluating reception ofdownlink data to obtain evaluation data. A step 730 comprisestransmitting the evaluation data in a second frequency band outside ofthe first frequency band. Method 700 may be performed, for example, bythe receiver 110.

FIG. 18 shows a schematic flowchart of a method 800 which may beperformed, for example, by the receiver 110 or by a transmitter. A step810 comprises receiving and processing a radio signal, the radio signalcomprising a first frequency band including a first signal, the firstsignal comprising a plurality of TDD-frames. A step 820 of method 800comprises transmitting data in a second frequency band outside of thefirst frequency band during a downlink-only subframe of a TDD-frame ofthe plurality of TDD-frames.

Embodiments described herein may be used in mobile communicationnetworks, in particular in enhanced mobile broadband (eMBB) services andultra-reliable low-latency communication (URLLC).

Although some embodiments have been described in connection withspecific LTE-configurations of resource allocations, otherconfigurations are also possible, for example, other uplink/downlinkconfigurations of frames and/or subframes.

Although some aspects have been described in the context of anapparatus, it is clear that these aspects also represent a descriptionof the corresponding method, where a block or device corresponds to amethod step or a feature of a method step. Analogously, aspectsdescribed in the context of a method step also represent a descriptionof a corresponding block or item or feature of a correspondingapparatus.

Generally, embodiments of the present invention can be implemented as acomputer program product with a program code, the program code beingoperative for performing one of the methods when the computer programproduct runs on a computer. The program code may for example be storedon a machine readable carrier.

Other embodiments comprise the computer program for performing one ofthe methods described herein, stored on a machine readable carrier.

In other words, an embodiment of the inventive method is, therefore, acomputer program having a program code for performing one of the methodsdescribed herein, when the computer program runs on a computer.

A further embodiment of the inventive methods is, therefore, a datacarrier (or a digital storage medium, or a computer-readable medium)comprising, recorded thereon, the computer program for performing one ofthe methods described herein.

A further embodiment of the inventive method is, therefore, a datastream or a sequence of signals representing the computer program forperforming one of the methods described herein. The data stream or thesequence of signals may for example be configured to be transferred viaa data communication connection, for example via the Internet.

A further embodiment comprises a processing means, for example acomputer, or a programmable logic device, configured to or adapted toperform one of the methods described herein.

A further embodiment comprises a computer having installed thereon thecomputer program for performing one of the methods described herein.

In some embodiments, a programmable logic device (for example a fieldprogrammable gate array) may be used to perform some or all of thefunctionalities of the methods described herein. In some embodiments, afield programmable gate array may cooperate with a microprocessor inorder to perform one of the methods described herein. Generally, themethods are performed by any hardware apparatus.

While this invention has been described in terms of several advantageousembodiments, there are alterations, permutations, and equivalents whichfall within the scope of this invention. It should also be noted thatthere are many alternative ways of implementing the methods andcompositions of the present invention. It is therefore intended that thefollowing appended claims be interpreted as including all suchalterations, permutations, and equivalents as fall within the truespirit and scope of the present invention.

1. A device comprising: an antenna; and a processor circuit, wherein theprocessor circuit is arranged to receive and process a radio signalusing the antenna, wherein the radio signal utilizes a first frequencyband, wherein the radio signal comprises a first signal, wherein thefirst signal comprises a plurality of time division duplex TDD-framesand downlink data, wherein the processor circuit is arranged to evaluatereception of the downlink data so as to acquire evaluation data, whereinthe processor circuit is arranged to transmit the evaluation data in asecond frequency band, wherein the second frequency band does notoverlap the first frequency band, wherein the processor circuit isarranged to transmit the evaluation data in at least a first uplinkchannel in the second frequency band, wherein the processor circuit isarranged to transmit the evaluation data at least a second uplinkchannel using a third frequency band, wherein the first uplink channeland the second uplink channel each comprise a bandwidth narrower thanthe first frequency band.
 2. The device of claim 1, wherein eachTDD-frame comprises a plurality of subframes, wherein a first subframeof the plurality of subframes is an uplink-only subframe or adownlink-only subframe.
 3. The device of claim 1, wherein each TDD-framecomprises a plurality of subframes, wherein the processor circuit isarranged to transmit the evaluation data during an downlink subframe inan uplink subframe of an NB-IoT frame.
 4. The device of claim 1, whereinthe second frequency band comprises a second signal, wherein the secondsignal comprises a plurality of TDD-frames.
 5. The device of claim 1,wherein the processor circuit is arranged to aggregate the first uplinkchannel and the second uplink channel by applying a common channel codeto the first uplink channel and the second uplink channel.
 6. The deviceof claim 1, wherein the first uplink channel and the second uplinkchannel are spaced from each other in the frequency domain.
 7. Thedevice of claim 1, wherein the processor circuit is arranged to acquirethe evaluation data, wherein the processor circuit is arranged todetermine a prediction value indicating a likelihood of error-freedecoding of the downlink data, wherein processor circuit is arranged tocompose a positive acknowledgement into the evaluation data when thelikelihood is above a threshold value, wherein processor circuit isarranged to compose a negative acknowledgement into the evaluation datawhen the likelihood is below the threshold value.
 8. The device of claim7, wherein the wherein processor circuit is arranged to transmit theevaluation data before processing of the received download data iscomplete.
 9. The device of claim 1, wherein the processor circuit isarranged to insert a positive acknowledgement indicating an error-freereception of the downlink data into the evaluation data or to insert,into the evaluation data, a negative acknowledgement indicating arequest for retransmission of the downlink data.
 10. The device of claim1, wherein the processor circuit is arranged to insert an indication ofan amount of additional redundancy for retransmission, wherein theindication is of a least one of a frequency, a time, a frame or a slotwithin a frame for retransmission, wherein information relating to achannel quality is determined by the processor circuit, whereininformation is related to a code block of the downlink data, wherein adecoding probability for retransmitted data comprising the additionalredundancy.
 11. The device of claim 1, wherein the processor circuit isarranged to transmit the evaluation data in response to a reception of aretransmission of the downlink data.
 12. The device of claim 1, whereineach TDD-frame comprises a plurality of subframes, wherein a subframe ofthe plurality of subframes is an uplink-only subframe or a downlink-onlysubframe, wherein the processor circuit is arranged to composeinformation indicating a request for using an uplink-only subframe intothe evaluation data.
 13. The device of claim 1, wherein the processorcircuit is arranged to operate in accordance with the LTE standard,wherein the second frequency band comprises an NB-IoT channel.
 14. Thedevice of claim 1, wherein the processor circuit is arranged to receiveevaluation data in the second frequency band responsive to atransmission of data in the first frequency band.
 15. The device ofclaim 1, wherein the first frequency band is used for a first mobilecommunication standard, wherein the second frequency band is used for asecond mobile communication standard.
 16. The device of claim 1, whereinthe processor circuit is arranged to transmit a control data in thefirst frequency band, wherein the control data indicates a position ofthe evaluation data in the second signal in the time domain or in thefrequency domain.
 17. The device of claim 1, wherein the processorcircuit is arranged to receive a control data in the first frequencyband wherein the control data indicates a position of the evaluationdata in the second signal in the time domain or in the frequency domain,wherein the processor circuit is arranged to transmit the evaluationdata at the position in the second signal.
 18. A device comprising: anantenna; and a processor circuit, wherein the processor circuit isarranged to receive and process a radio signal using the antenna,wherein the radio signal utilizes a first frequency band, wherein theradio signal comprises a first signal, wherein the first signalcomprises a plurality of time division duplex TDD-frames and downlinkdata, wherein the processor circuit is arranged to evaluate reception ofthe downlink data so as to acquire evaluation data, wherein theprocessor circuit is arranged to transmit the evaluation data in asecond frequency band, wherein the second frequency band does notoverlap the first frequency band, wherein the processor circuit isarranged to transmit control data related to a resource allocation ofthe first signal to indicate a position of the evaluation data or otherdata in the second signal in the time domain and/or in the frequencydomain or the processor circuit is arranged to transmit user datatogether with the evaluation data.
 19. A device comprising: an antenna;and a processor circuit, wherein the processor circuit is arranged toreceive and process a radio signal using the antenna, wherein the radiosignal utilizes a first frequency band, wherein the radio signalcomprises a first signal, wherein the first signal comprises a pluralityof time division duplex TDD-frames and downlink data, wherein theprocessor circuit is arranged to evaluate reception of the downlink dataso as to acquire evaluation data, wherein the processor circuit isarranged to transmit the evaluation data in a second frequency band,wherein the second frequency band does not overlap the first frequencyband, wherein the processor circuit is arranged to transmit scheduledata, wherein the schedule data indicates a schedule of a NB-IoT nodetransmitting in the second frequency band, wherein the processor circuitis arranged to generate the schedule data so as to schedule thetransmission of the NB-IoT node to an uplink subframe of a second signalin the second frequency band, wherein the uplink subframe unused fortransmission.